On the LT&S the changeover point was just east of Barking station on both Upminster and Tilbury routes with the link to Forest Gate being at 6.25kV ac.

Public service started on 16 March 1959 with Class 302s working the first electric passenger trains between Colchester and Clacton at 25kV ac.

[18] They were among the first electric units delivered to the Eastern Region and, although ordered for the LT&S electrification, a route they were long associated with, they were used initially on the Liverpool Street to Hertford East, Bishop's Stortford and Enfield Town lines when they were electrified in November 1960.

The 302s also stepped in when electrification was extended from Chelmsford to Colchester in 1961 and when the Class 305 units were having problems on the then new north-east London electric services.

[16] The first 25 units remained on the GE main line for the bulk of their lives, with the remainder operating on the LT&S from Fenchurch Street from 1962.

[20] Unit 302 244 was involved in an accident in 1972 with a lorry at a level crossing at Low Street railway station in Tilbury, after which it was decided to scrap the leading carriage, BDTC 75292.

[20][19][21] In 1987–88, 6 units were short formed with the removal of the trailer composite (TCsoL) and based at Ilford EMD for work on the GE lines.

The motor coach retained its Gresley derived bogies after refurbishment with compartments removed for an open layout with guards van.

[32] [33] When introduced, the units were outshopped in plain BR EMU suburban green livery with the early lion and wheel crest on the MBS.